The present invention relates to a detecting apparatus for detecting a fine geometry (an image) on a surface of a sample by irradiating an irradiation beam against the sample and then detecting and processing a secondary radiation emanated from the sample. The fine geometry on the surface of the sample, for the purpose of the present invention, includes a defect in such a high density pattern having a minimum line width of 0.15 μm or smaller formed on a wafer surface of a semiconductor device, for example. The present invention also relates to a manufacturing method of a semiconductor device employing such a detecting apparatus.
There has been known such a detecting apparatus which comprises an electron gun for emitting an electron beam into a vacuum chamber, an illuminating optical system consisting of a series of electrostatic lenses, a stage for carrying a wafer to be inspected, a map projecting optical system consisting of a series of electrostatic lenses, and a sensor. This known detecting apparatus further comprises an MCP (Micro Channel Plate) for amplifying detected electrons, a fluorescent screen for converting the amplified electrons into a light, an FOP (Fiber Optic Plate) functioning as a relay between a vacuum system within a vacuum chamber and an external component for transmitting the optical image converted by the fluorescent screen, and an image-taking device such as a CCD (Charge Coupled Device) for capturing an optical image output from the FOP, wherein the vacuum system within the vacuum chamber is hermetically sealed against an external environment but an electric signal can be transmitted from the inside of the vacuum chamber to the outside thereof.
FIG. 1 and FIG. 2 show schematic diagrams illustrating prior art detecting apparatuses. A detecting apparatus of FIG. 1 comprises a vacuum vessel 20 for accommodating a sample 10, or a semiconductor wafer, for example, a hermetic glass plate 21 transparent to the light emitted from the sample, a lens 31 disposed in the atmosphere, a sensor 32, and a camera 33. An image signal for the sample generated in the sensor 32 is input to the camera 33 and converted into image data. The image data is used in a defect inspection for the sample by a comparative method among dies, that is, a method in which the comparison is applied among pattern images obtained from the corresponding regions (observational screens) of the dies (chips) aligned on different wafers (see JP-A-5-258703, JP-A-6-188294).
A detecting apparatus 2 shown in FIG. 2 is similar to the detecting apparatus of FIG. 1 with the exception that a sample 10 of FIG. 2 emanates secondary electrons 11, which in turn are converted into a light by a fluorescent screen 19. Specifically, in the detecting apparatus of FIG. 2, the secondary electrons 11 emanated from the sample 10 by irradiating a primary electron beam against the sample 10 are introduced into the fluorescent screen 19 via an electronic optical system having a lens 12 and an amplifier 13, and then the electrons 11 are converted into the light by the fluorescent screen 19. The light from the fluorescent screen 19 is guided out of a vacuum vessel 20 through a hermetic glass plate 21 and passes through a lens 31 to be introduced into a sensor 32. The sensor 32 generates an image signal for the sample, which in turn, is input to the camera 33 to be converted into image data.
However, the prior art detecting apparatus shown in FIG. 1 and FIG. 2 has such a drawback that the intensity of the light reaching the sensor has been attenuated since in this apparatus the light beam passes through the hermetic glass plate defining the inside and outside of the vacuum vessel and also through the lens and then enters the sensor in the atmosphere so as to be converted into the image signals for the sample surface. The attenuation factor of this configuration is observed to be, for example, in the range of 1/20 to 1/2. In addition to the problem of the attenuation occurring in the intensity of the light, the prior art detecting apparatus also has another problem that the hermetic glass plate and/or the lens may cause an aberration or distortion in the light beam, inhibiting the capturing of highly accurate image. Furthermore, the prior art apparatus still has another problem that use of many optical components and supporting and/or fixing parts thereof in the apparatus might sometimes cause a mechanical offset among the sensor, the hermetic glass and the lens, which also inhibit the capturing of highly accurate image.
Further, the apparatus shown in FIG. 2 using the conventional electronic optical system, in which the image information represented by the electrons is converted into light and then thus converted light is in turn detected, is also problematic in that the efficiency and resolution may deteriorate as a result of this conversion. An object of the present invention is to provide a detecting apparatus which provides a solution to the problems pertaining to the apparatuses according to the prior art. In specific, the object of the present invention is to improve a resolution and a throughput of inspection of a detecting apparatus for detecting a fine geometry (an image) on a surface of a sample by, in an environment different from that of the atmosphere, irradiating an irradiation beam against the sample and then detecting and processing a secondary radiation emanated from the sample. These and other objects of the present invention will be apparent from the description described below.